Retinoids such as cis-retinoic acid (RA) have a broad spectrum of activity in causing growth inhibition and differentiation in normal tissue and in a number of pediatric malignancies in vitro. In patients, both all-trans- retinoic acid (ATRA) and 13-cis-retinoic acid have been used, although with a different spectrum of anti-tumor efficacy. Some theoretic considerations and some laboratory data suggest that 9-cis-RA may be more potent than other of the retinoids as an anti-tumor agent. This proposal uses a standard phase I design and pharmacokinetics.